Tension shoe member for film sprockets



April 1 1951 E. J. WIENKE 2,549,271

TENSION SHOE MEMBER FOR FILM SPROCKETS Filed Feb. 15, 1946 [Til/6712. 07 52112 J Zflzlerne 59 g ga Patented Apr. 17, 1951 TENSION SHOE MEMBER FOR FIL SPROGKETS EmilJ. Wienke, Glen Ellyn, Ill., assignor to M- tiograph, Chicago, 111., a limited partnership Application February 15, 1946, Serial No. 647,940 1 Claim. (01. 271-23) principal purpose of my invention to provide an improved tension shoe construction whereby the shoe can be readily retracted and quickly released to return to tension position. 1.

It i also a purpose of the invention to provide a tension shoe construction whereby l the pressure of the shoe on the film is balanced at all times.

The nature and advantages of my invention I will appear more fully from the following description and the accompanying drawings) It should be understood, however, that the drawings and description are illustrative only,and should not be considered a limiting the invention except insofar as it is limited by the claim.

In the drawings:

Figure l is a fragmentary sectional view through a projector intermittent sprocket showing my invention as applied thereto,

Figure 2 is a fragmentary view looking at Figure 1 from the line 22, and

Figure 3 is a sectional view on the line 3-3 of Figure 1.

Referring now to the drawings, the intermittent sprocket 5 of the projector is driven by the shaft 6 in any suitable manner. The sprocket is mounted by two bearings I and-8 at its opposite ends, these hearings forming part of an intermittent sprocket support 9 which also has a post 10. that is substantially rectangular in cross section and extends out past the center line of the sprocket 5. The sprocket 5 has two toothed sections II and [2 which guide the film I 3, and advances it by engaging the teeth through the apertures provided .at the side edges of the film. In order to hold the film tight against the sprocket, I provide two spaced apart film engaging shoes l4 and IS, the faces of which are arcuate about the axis of the shaft 6 as a center when the shoes are engaged with the film on sections H and I2. The shoes are formed on the legs of a U-shaped member 16, the central portion of which has a boss I I that is engaged by a spring [8.

The support IQ for the member l6 has four legs, 20, 2|, 22 and 23. The legs of the U -shaped member l8 have pins 24 fastened therein, and

these pins have heads 25 that ride in slots 26 that are formed in the legs 20, 2|, 22 and 23. The member H] has a central stem portion 21 that is provided with a recess 28 to receive the spring I 8. The spring I8 is under compression so that it tends to force the member l6 toward the intermittent sprocket to the full extent of its movement with respect to the member l9. This movement is of course governed by the length of the slots 26 provided in the legs 20, 2|, 22 and 23. The tension of the shoes I 4 and I5 on the film is governed by the spring [8 which may have any suitable tension for the purpose. The entire member IS with the shoe I6 is movably mounted on the lug ID. This mounting is provided :by the stem 21 which is set in a recess of the lug Ill. The stem is held in place by a plate 29 that is fastened to the lug In by two screws 30. Two springs 3| and 32 are set into recesses in the lug H] on opposite sides of the stem 21 so as to urge the assembly toward the intermittent sprocket. Finger piece 33 and 34 are provided on the member IQ for the operator to grasp to pull the tension shoe and member 19 away from the intermittent sprocket.

The member 19 and the associated tension shoes are locked in retracted position by a releasable mechanism which comprises a ball detent 35 seated in a recess 36 on the lug I0. and backed up by a pring 31. This ball 35 is adapted to seat in a V-shaped recess 38 provided in the stem 21 when the stem is retracted to the position shown in Figure 3. Release pin 39 is mounted in the stem 21. the tip being guided in an aperture 40. This aperture is enlarged to form a spring pocket 4| for a spring 42 that normally holds the pin 39 retracted. A collar 43 on the pin 39 abuts the plate 29 to limit the retractive movement of the pin 39. An operating stem 44 projects through a slot 45 in the plate 29 from the collar 43 and has a head 46 thereon.

The operation of the device is as follows:

Assuming that it is desired to thread a film around the intermittent sprocket 5, the operator engages the finger pieces 33 and 34 and withdraws the member 19 and the tension shoes l4 and I5 from the position shown in Figure l to the position shown in Figure 3. In this position the ball 35 snaps into the V-slot 38 looking the parts in retracted position. The film is then threaded over the intermittent sprocket as desired. After floating in the sense that all of the spring pressure upon them is applied at the centralpoint I1, so that the tension Will be uniformly distributed ibe-fl tween the two shoes and along the length of the Having thus described my invention, I claim:' In a film tension device for film sprockets, a

tension shoe member having means for engaging shoes.

a film on the sprocket, a support for said member, means mounting the member on the support for limited movement toward and away from the sprocket, spring means mounted between the support and the member urging the me'mber'toward the sprocket, a mounting means for the support mounting it for limited movement toward and away from the sprocket, and spring means between the mounting means and the support urging the support toward the sprocket.

' EMIL J. WIENKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,o73, 224 Ross Mar. 9, 1937 2,178,208 Loomiset a1 Oct. 31, 1939 2,228,092 "Sperry Jan. '7, 1941 2,369,089 Thomas Feb. 6, 1945 2,413,545 Zimmerman Apr. 8, 1947 FOREIGN PATENTS Number Country Date' 37,471 France Sept. 9, 1930 708,112 France Apr. 27, 1931 

